Aluminum alloy rivet



Patented'Aug. 12, 1941 UNITED STATES PATENT OFFICE I v J ALUMIN U M liizlY RJWET Hans Bothmann, Aken, and Walter Mannchen,

Dessau, Anhalt, Germany, assignors, by memo assignments, to Walther H. Duisberg, New York,-

No Drawing. Application October 17, 1930, Serial No. 299,808. In Germany September 29, 1938 3 Claims.

alloys have the advantage of a high shearing strength of about 2'1 kilograms per sq. mm. in the hardened state, but they have the drawback that, after the usual annealing at about 500 C. and more and subsequent quenching, the ensuing precipitation takes place relatively rapidly and thus causes a correspondingly rapid hardening of the alloys. used immediately after the heat treatment in order to avoid the formation of shearing cracks during the riveting process due to excessive hardness of the alloys.

The period which may be allowed to elapse with alloys of the type in question after completion of the heat treatment before riveting same without formation of shearing cracks is hereinafter termed the-Potential time of storage" and it is the main object of the present invention to provide age hardenable alloys of the type Al-Ou-Mg especially for riveting purposes which will combine high mechanical strength properties and particularly high shearing strength. in the hardened state with a relatively long potential time of storage.

The present invention is based on the observation that the speed of hardening of heat-treated The rivets must, therefore, be

nesium substantially unchanged which ratio is generally regarded as the best for obtaining a high shearing. strength in the hardened rivets.

In accordance with the invention the aluminum base alloys contain, besidesaluminum, about 3.5 to 4.5 per cent of copper. about 0.4 to 1.4 per cent of magnesium, 0.3 to 0.7 percent of manganese and, furthermore, iron and silicon and are characterized in that the content of iron is more than 5 times as great as that of silicon and does not exceed about 0.6 per cent. 4

Preferably the silicon content is kept below I about 0.05% whilst the iron content is preferably at least about 0.4%. Suitable riveting alloys according to the invention are, for instance, the

7 following:

Number Composition in per cent Shearin 'strongtha ter Maxi storsge,in a kilos storage Cu Mg Mn Si Fe squggtgilll- 20 0 Hours 1 3.70 1.34 0.40 0.016 0.40 27.2 2 4.00 0.92 0.40 0.03 0.49 27.2 14

alloys of the type Al-Cu-Mg depends to a great extent on the proportion prevailing between the iron and the silicon content of the alloy. It has been found that the potential time of storage is considerably increased, in comparison with alloys which are composed according to the aver age ranges of composition above set forth, if the proportion of the iron to the silicon is more than about 5 to 1, and the content of iron does not exceed 0.8.per cent of, the total alloy. If these proportions are maintained precipitation in the alloys occurs at such a rate that there is sufiicient time left after heat-treatment to use the alloys successfully under practical shop-working conditions, the potential time of storage being about 10 hours. On the other hand it is possible, when the ratio of iron and silicon is chosen accordingly, to keep the ratio of copper and mag- Even when the alloys are stored at a somewhat elevated temperature instead of normal temperature, the potential time of storage is not shortened so much as to render the riveting of the alloys within a reasonable period after completion of the heat treatment impossible.

What we claim is: v

1.. An aluminum base alloy containing between about 3.5 and about 4.5 percent of copper, between about 0.4 and about 1.4 per cent of magnesium, between about 0.3 and about 0.7 per cent of manganese and also iron and silicon, the content of the iron not exceeding 0.6 per cent of the total alloy while being more than five times as great as that of the silicon, the balance of the 2. An aluminum base alloy containing between 0 about 3.5 and about 4.5 per cent of copper, between about 0.4 and about 1.4 per'centof magnesium, about 0.7 per cent of manganese and also iron and silicon, the content of the iron not exceeding about 0.6 per cent of the total alloy while being more than five times as great as that of the silicon, thebalance of the alloy being substantially all aluminum, said alloy being characterized by its capacity for being age-hardened and by high mechanical strength properties, particularly high shearing strength, in the hardened state, and by its relatively long potential time of storage. i

3. An aluminum basealloy containing between about 3.5 and about 4.5 per cent of copper, between about 0.4 andabout 1.4 per cent oi magnesium, about 0.7 per cent of manganese and also iron and silicon, the content of the iron not exceeding about 0.6 per cent and amounting to at least about 0.4 per cent and the content of the silicon not exceeding about 0.05 per cent of the total alloy, the balance of the alloy being substantiaily all aluminum, said alloy being characterized by its capacity for being age-hardened and by high mechanical strength properties, 

